Apparatus for in-situ soil remediation

ABSTRACT

An apparatus for in-situ remediation of contaminated soil or sludge having a trenching tool and an injection system for applying remediation agent to the contaminated material during in situ communication. The remediation agent is injected into the contaminated material by the injection system preferably having a plurality of injection nozzles positioned along the length of the trenching tool. The treated material is backfilled or deposited directly into the trench excavated by trenching tool thereby obviating the need for off-site disposal. The constituent remediation agents in the remediation agent may be adjusted to adapt to varying site conditions and contaminants. The remediation agent may also be heated to accomplish volatile stripping of the contaminated material or to activate microbial agents in a low temperature environment.

This is a Divisional of application Ser. No. 08/287,275, filed Aug. 8,1994 and issued as U.S. Pat. No. 5,631,160 on May 20, 1997, which is acontinuation-in-part of U.S. patent application Ser. No. 08/057,342,filed May 3, 1993, now abandoned.

FIELD OF THE INVENTION

The invention relates to a method and an apparatus for the in situremediation of contaminated soil or sludge.

BACKGROUND OF THE INVENTION

It is widely recognized that years of unregulated industry have producednumerous environmentally hazardous sites throughout the country and theworld which pose substantial health hazards to world's population. Inrecent years, efforts to clean up or remediate environmentallycontaminated sites have increased dramatically, and numerous methods anddevices for cleaning up or disposing of environmental contamination havebeen devised or proposed. However, the magnitude of the environmentalproblems is enormous, but the resources available to solve the problemsare limited. Therefore, there is an urgent need for methods ofremediation that are relatively uncomplicated, may be rapidlyimplemented, and are technically and cost effective.

Therefore, it is an object of this invention to provide a costeffective, relatively rapid method of remediating environmentallycontaminated sites.

It is another object of this invention to provide a highly mobileapparatus for remediating environmental contaminants.

It is yet another object of this invention to provide a method ofremediating contaminated soil in situ and without removal or disposal ofthe treated or contaminated material.

It is yet another object of the invention to provide a method that iscapable of remediating contaminated soils and sludges in a continuous,in contrast to a batchwise, manner.

It is yet another object of the invention to provide a remediationapparatus and method which may be used on highly unstable soils and intight quarters such as in the basements of buildings or nearabove-ground or below-ground storage tanks.

The above objects and advantages of the present invention will becomemore apparent when reference is made to the following description takenin conjunction with the accompanying drawings.

SUMMARY OF THE INVENTION

Contaminated material such as soil or sludge is remediated by injectinga suitable remediation fluid into the material during excavation of thecontaminated material with a trenching tool. The remediation fluid isinjected into the contaminated material through an injection means,preferably a plurality of injection nozzles positioned along the lengthof the trenching tool. The thusly treated material is backfilled ordeposited directly into the trench excavated by the trenching toolthereby obviating the need for off-site disposal. The constituentremediation agents in the remediation fluid may be adjusted to adapt tovarying site conditions and contaminants. The remediation fluid may alsobe heated to accomplish volatile stripping of the contaminated materialor to activate microbial agents in a low temperature environment.

In one aspect, the present invention is an injection treatment apparatusfor remediating contaminated material at a contaminated site having atrenching mechanism means with a trenching tool and a means forpositioning and powering the trenching tool. The apparatus has aninjection means for injecting a remediation fluid into the contaminatedmaterial in close proximity to the trenching tool and a remediationfluid delivery means for conveying and delivering the remediation fluidto the injection means under pressure.

The injection means has at least one injection nozzle, preferably aplurality of injection nozzles, positioned to inject the remediationfluid into contaminated material excavated during operation of thetrenching tool. The injection nozzles are preferably located atpredetermined positions along the length of the trenching tool.

The remediation fluid delivery means has a remediation fluid storagemeans, a conduit means and a pump means for pumping the remediationfluid from the storage means through the conduit means to the injectionmeans under pressure. Optionally, the remediation delivery means mayhave a heating means for heating the remediation fluid such as in thecase of forced hot air.

The apparatus may also have a monitoring means for monitoring a selectedphysical or chemical property of the contaminated material such as pH,oxygen content, temperature or the like in the proximity of thetrenching tool during operation of the apparatus and a means foradjusting the selected property of the contaminated material to apredetermined value, such as a means for adjusting the amount of aconstituent remediation agent in the remediation fluid injected into thecontaminated material during operation.

The apparatus may also comprise a volatile collection means forcollecting volatile substances such as volatile hydrocarbons emittedfrom the contaminated material during treatment with the injectiontreatment apparatus.

In another aspect, the invention comprises a method for remediating acontaminated material at a contaminated site. The method comprisesagitating the contaminated material with a trenching tool mechanismhaving a trenching tool and contemporaneously injecting a suitableremediation fluid into the agitated or excavated contaminated materialin the proximate vicinity of the trenching tool to provide a treatedmaterial. The treated material is preferably deposited into the trenchexcavated by the trenching tool mechanism.

Where the contaminated material comprises a volatile constituent, theremediation fluid is preferably a fluid such as hot air for volatilizinga volatile constituent which is then collected using a collection means.In the case of a liquid or semi-solid contaminated material such as asludge or wastewater lagoon, the remediation fluid preferably comprisesa solidification agent which is injected into the contaminated materialthereby solidifying it and permitting further treatment. The method mayalso comprise monitoring a selected physical or chemical property of thecontaminated material such as pH, oxygen content, temperature or thelike and adjusting the selected property of the contaminated material toa predetermined value such as a value determined necessary or sufficientto environmentally remediated the contaminated material. For example,the pH may be maintained at a predetermined value by adjusting theamount of a constituent pH adjusting agent such as a pH buffer solutionin the remediation fluid. The method may also comprise the step ofheating the remediation fluid prior to injecting it into thecontaminated material. This is useful where the remediation fluidcomprises a microbial bioremediation agent and a gas such as air isheated sufficiently to activate the bioremediation agent in thecontaminated material in a low temperature environment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation of the trenching tool portion of thetrenching tool mechanism and the injection means.

FIG. 2 is a sectional view taken through line 2--2 of FIG. 1.

FIG. 3 is a schematic diagram of a trenching tool mechanism excavatingcontaminated soil and injecting a remediation fluid along the length ofthe trenching tool.

FIG. 4 is a schematic diagram of another embodiment of a trenching toolmechanism excavating contaminated soil and injecting a remediation fluidalong the length of the trenching tool.

FIG. 5 is a side elevation of another embodiment of the trenching toolportion of the trenching tool mechanism and the injection means.

FIG. 6 is a side elevation of the injection or evacuation manifold.

FIG. 7 is an enlarged view of an injection or evacuation port of themanifold.

FIG. 8 is a schematic view of the carbon filter of the evacuation systemof the apparatus.

FIG. 9 is a schematic view of a large-scale soil remediation apparatusaccording to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In describing a preferred embodiment of the invention illustrated in thedrawings, specific terminology will be used for the sake of clarity.However, the invention is not intended to be limited to the specificterms so selected, and it is to be understood that each specific termincludes all technical equivalents which operate in a similar manner toaccomplish a similar purpose.

With reference to the drawings, in general, and FIGS. 1 through 3 inparticular, a trenching tool mechanism 10, injection means 41 andremediation fluid delivery means are shown.

The trenching tool mechanism 10 includes a mobile unit 20 mounted ontracks 21 having a boom 22 and hydraulic piston cylinder assemblies 24and 26 for positioning trenching tool 30. Injection system 41 havinginjection nozzles 40 is mounted along the length of shaft 36 oftrenching tool 30. The injection nozzles 40 are positioned below aplurality of digging tools 32 mounted on conveyor chain 34. As can beseen from the drawings, the injection nozzles are positioned such thatthe remediation fluid is injected below the soil surface while thecontaminated soil is being excavated or comminuted by the trenchingtool. The remediation fluid is thereby injected in the trench in theimmediate vicinity of the excavation or comminution of the contaminatedsoil along the trenching tool. In operation, conveyor chain 34 is drivenabout sprockets 44 at the ends of shaft 36. The trenching tool 30 iscapable of excavating a trench of 3 to 30 feet in depth. The mobile unit20 may be any suitable equipment such as a skid loader, backhoe,excavator, gradall or the like. The size of the trenching tool andmobile unit will vary depending upon site conditions.

The remediation fluid is pumped from storage tank 12 through conduit 14to injection system 41 under pressure by a pump (not shown). Theinjection pressure may vary from about 10 psi to about 3,000 psidepending upon the desired remediation treatment. The remediation fluidmay also be heated by a heating unit (not shown). The size and number ofthe injection nozzles may vary in accordance with the remediationtreatment. For example, the nozzle size for pressurized hot air mayrange from about 1" to about 4" in diameter. Nozzle size for injecting ahigh pressure liquid may be 1/4" or smaller. The injection system may bepressurized by any suitable power source such as a hydraulic, electricor diesel power unit.

The remediation fluid delivery system may comprise a mixing unit formixing constituent remediation agents from a plurality of storage tanks.Alternatively, parallel systems for delivering and injecting a pluralityof remediation fluids may be employed. Such an embodiment isparticularly useful, for example, when two or more different remediationfluids such as a gas and a liquid are being injected into thecontaminated soil simultaneously. The parallel system permits themultiple fluids to be injected through injection nozzles of differentsizes at different pressures.

With reference to FIGS. 4 through 7, in a preferred embodiment, theremediation fluid may be injected adjacent to conveyor chain 34 anddigging tools or teeth 32 from manifold 80 positioned lengthwiseparallel to shaft 36. The remediation fluid is injected throughinjection ports 82. Alternatively, the ports may be plugged with portplugs (not shown) and end cap 84 at end 83 of manifold 80 may be removedto allow injection solely in the bottom of the trench. Optionally, avideo camera 94 may be mounted on trencher tool housing 90 or,alternatively, at end 83 of manifold 80. A monitor mounted in the cab ofmobile unit 20 and attached to camera 94 permits the operator to viewthe injection and trenching activity within the trench.

In operation, the contaminated soil 60 is excavated, and therebycomminuted and agitated, by trenching tool 30 in the direction of arrow50. During excavation, a suitable remediation fluid is pumped throughinjection nozzles 40 of injection system 41 into the contaminated soil.The treated soil 55 is discharged into the trench thusly excavated bytrenching tool 30 behind trench guard 42. A wide area of contaminatedmaterial such as contaminated soil or sludge at a site may be treated bytrenching in parallel rows or any other suitable pattern across theentire area.

Preferably, after an initial trench is excavated, a trench immediatelyadjacent to the initial trench is excavated and injected withremediation fluid. The thusly treated soil falls or is discharged to theside of the new trench line into the void of the initially excavatedtrench. Each subsequent trench is then excavated immediately adjacent tothe preceding trench. In this manner, the soil is treated in situwithout removing any significant amounts treated or contaminated soilabove the ground level or surface of the contaminated material 56. Onlya minimal amount of treated and untreated soil is exposed to theatmosphere, since only one trench line is exposed at any given moment.

Alternatively, the treated soil may be returned into the trench which iscurrently being excavated. This can be achieved by excavating the soil(which has been treated by injection) with the trenching tool andconveying it by cross and return conveyors 100 as illustrated in FIG. 9and the like to an open portion of the trench. The use of cross andreturn conveyors to backfill a trench is known and will be apparent toone skilled in the art. Soil treated by injection is deposited on across conveyor and then transferred to return conveyor 100 anddischarged through chute 102 into the trench behind trenching tool 30(not shown). Preferably, bank guard 104 is attached to trenching tool 30to prevent the collapse of the trench walls. Backfilling may be requiredwhere a large scale trenching tool and tractor are employed asillustrated in FIG. 9, since as a practical matter the size of thetrench may not permit the tractor to position the trenching toolimmediately adjacent to the first trench without the tractor fallinginto the trench. When the treated soil is backfilled, it is preferredthat the cross and return conveyors be enclosed or shrouded to minimizeexposure of the soil to the atmosphere.

Any suitable remediation fluid, such as gases, liquids, slurries, orparticulate solids, may be injected into the contaminated material inaccordance with the process of this invention. The choice of remediationfluid and its constituents will depend upon site conditions and thecontaminants sought to be remediated. By way of example, and withoutintending to be limited thereto, a liquid lime solution may be injectedto stabilize a lead-contaminated site. A liquid biostimulant such asPOLYBAC-N™, POLYBAC-E™ and appropriate microorganism such as HYDROBAC™,PETROBAC™, and PHENOBAC™ are sold by Polybac Corp. of Bethlehem, Pa. maybe injected to treat contaminants such as mineral oil, glycol orchlorinated phenols. Other suitable bioremediation fluids and nutrientinclude, for example, the white rot fungi and enzymes disclosed in U.S.Pat. Nos. 4,891,320 and 5,085,998, the disclosures of which are hereinincorporated by reference, and the corresponding biostimulants includinglignin, cellulose, wood shavings, sawdust, corn cobs, and humusdisclosed therein. The remediation fluid may also comprise variousencapsulating or zeolitic compounds and compositions such as ZEOMIX™available from Pacific Summa Corp through its distributor,Shefford-Mead, of West Chester, Pa. Other suitable remediation fluidsand reagents include alkali constituents and sulfoxide catalystdisclosed in U.S. Pat. No. 4,447,541, the aqueous silicate solutions andfixatives disclosed in U.S. Pat. No. 4,687,373, and calciumorthophosphate agents and other remediation constituents disclosed inU.S. Pat. No. 5,162,600, the patent disclosures of which are separatelyincorporated herein by reference. Sludges may be solidified by injectinga solidification agent such as kiln dust into the contaminated sludge.If desired, a variety of remediation agents may be used in combination.For example, an oxygenation agent such as grade D breathing air may beused in combination with a bioremediation agent to aerate and acceleratethe treatment of the contaminated material.

Stripping of volatile contaminants such as acetone, toluene, isopropylalcohol, trichloroethanol, and the like may be accomplished by injectinghot air under pressure to volatilize the contaminants. The volatilecontaminants may be collected by any suitable collection system such asa tent-like structure having a positive pressure circulation system witha carbon filter. Such a collection system is available from SprungStructures, Inc. of Allentown, Pa. The apparatus of the presentinvention may be sized to operate within the tent-like structure.

In a preferred embodiment, hot air is injected under pressure throughinjection manifold 80. The air is supplied by a blower such as is knownin the environmental remediation arts for use in volatile strippingwhich heats the temperature of the air to between 200°-300° F. It ishowever preferred to increase the hot air temperature to well above thisconventional temperature range by further heating the air with asupplemental heating element. For example, the exhaust of a dieselpowered excavator may be used to raise the temperature to between 400°and 550° F. This permits the volatilization of hydrocarbon substanceswhich would not be otherwise remediable by conventional volatilestripping. The comminution of the soil by the trenching tool also servesto reduce the density of non-porous or slightly porous soil types whichwould not otherwise be treatable by conventional volatile strippingmethods.

When hot air is injected into the soil, the emissions are preferablyrecovered to prevent release into the atmosphere. The present inventionprovides for an emissions evacuation system to collect emitted gases.With reference to FIGS. 4 and 5, a trencher tool housing 90 may befitted about end 99 of shaft 36. Housing 90 may comprise flexible skirt92 to prevent the release of gases under the perimeter of the housing. Anegative pressure evacuation system (not shown) may be fitted to port 96to draw released gases to a filter such as a carbon canister filter 110(FIG. 8). the gas enters the filter through port 112 and the filteredgas is exit through port 114. Preferably when hot air is being injectedinto the soil, the filtered hot air is recirculated back to the blowerfor subsequent injection into the trench area through the injectionsystem.

In another embodiment, the hot air may be injected through port 96 inthe proximity of chain 34 at chain gear drive 98 at end 99 of shaft 36.The evacuation system may then be connected to manifold 80 and thereleased gases are evacuated through ports 82. In yet anotherembodiment, the hot air is injected through the end of a second manifoldpositioned parallel to manifold 80 at the bottom of the trench while theevacuation system is collects released gases through manifold 80. Thehot air is thereby injected in the bottom of the trench as the soil isbeing comminuted.

The present invention may be used to remediate contaminated sites whichwere heretofore untreatable. For example, bioremediation of contaminatedsoil may not, in general, be achievable in low temperature environments,typically environments having temperatures below about 40° F. The lowtemperatures tend to incapacitate or kill the microorganisms thataccomplish the remediation. However, the present method provides for theinjection of a heated gas such as hot air in combination with thebioremediation agent thereby raising the temperature at the locus oftreatment and activating the bioremediation agent. This has thebeneficial effect of permitting bioremediation of contaminated soils incooler or arctic climates and/or extending the effective season duringwhich bioremediation may be accomplished in temperate climates.

In another instance, the present invention provides for the injection ofremediation fluids in dense, clay-laden soils. The prior art methods ofinjection are ineffective in treating non-porous, clay-laden soils,because the injected remediation fluid is unable to migrate throughoutthe soil. However, according to the present invention, clay-laden soilsmay be effectively remediated, because the method comminutes the soilduring excavation by the trenching tool.

The present invention is principally intended for the treatment ofcontaminated soil. However, a wide variety of contaminated materials,including semi-solid sludges and wastewater lagoons, may be treated inaccordance with the invention. In the case of a lagoon, the injectiontreatment apparatus may act as a kind of large-scale, mobile mixer foragitating and injecting a remediation fluid into the wastewater. Thewastewater may be first treated to neutralize contaminants in the water,and subsequently treated with a solidification agent. Alternatively, thewastewater may be first injected with a solidification agent to form acontaminated "soil", and then injected with a second remediation fluidto neutralize the contaminants.

EXAMPLES

The following examples are illustrative of the process of the presentinvention but are not intended to limit the scope of the presentinvention.

Example 1

A soil contaminated by machine oil leaked from heavy equipment issubject to a treatability study to determine appropriate bioremediateagents and nutrients for the bioremediation of the soil. It isdetermined that hydrogen-degrading bacteria HYDROBAC™ and nutrientsPOLYBAC-N™ available from Polybac of Bethlehem, Pa., are suitable toremediate the contaminated soil. The contaminated site is laid out ingrids and each grid is treated by injecting sufficient POLYBAC-N to thedepth of the contamination up to 12 feet using the apparatus of thepresent invention to insure sufficient levels of nitrogen andphosphorus. During an eight week period, the HYDROBAC product with wateris injected at periodic intervals using the apparatus of the invention.To provide ample oxygen, air is injected in the soil by the apparatus ona daily basis. Bacterial growth and activity are monitored on a weeklybasis and adequate nutrient concentrations and pH are maintained in thesoil at all times through the injection of required substituents(bacteria, nutrients or water) at all times.

Example 2

The slow leakage of VARSOL™, a solvent comprised of mineral spirits andnaphtha, from a drum storage area resulted in a gradual release andinfiltration of petroleum hydrocarbons into underlying soil. Thecontamination consisted of approximately 2500 cubic yards in groundhaving a Total Petroleum Hydrocarbons ("TPH") content in the range of4444 ppm to 16268 ppm. The site area was divided into several work areagrids. A chain type trenching tool was mounted on the boom of aexcavator and an injection manifold was installed. Each grid wasprocessed with by injecting forced hot air at a temperature of 350°-480°F. below the groundlevel surface while trenching to a depth ofapproximately twelve feet in parallel rows within each grid. Anemissions evacuation system comprising a evacuation manifold positionedadjacent and parallel to trenching chain was used to evacuate noxiousemissions. Air monitoring was performed on the vapor recovery system ofthe processing apparatus as well as background areas to determine theextent of emissions, if any. At the end of the processing, TPH levelswere reduced to less than 5 ppm throughout the site. No significant airemissions were detected.

Although this invention has been illustrated by reference to specificembodiments, it will be apparent to those skilled in the art thatvarious changes and modifications may be made which clearly fall withinthe scope of the invention. The invention is intended to be protectedbroadly within the spirit and scope of the appended claims.

What is claimed is:
 1. An apparatus for remediating a contaminatedmaterial in-situ at a contaminated site, said apparatus comprising:atrenching mechanism comprising an in-situ mechanical trenching tool forcomminuting contaminated material; an injection system for injecting aremediation agent into the contaminated material in close proximity tothe trenching tool comprising at least one injection nozzle positionedand adapted to inject the remediation agent below the surface of thecontaminated material while the material is being comminuted by thetrenching tool; and a remediation agent delivery system for conveyingand delivering the remediation agent to said injection system.
 2. Theapparatus according to claim 1, wherein said injection system comprisesat least one injection nozzle positioned to inject said remediationagent into said contaminated material during operation of said trenchingtool.
 3. The apparatus according to claim 2, wherein said injectionsystem comprises a plurality of injection nozzles.
 4. The apparatusaccording to claim 3, wherein said injection nozzles are located atpredetermined positions along the length of said trenching tool.
 5. Theapparatus according to claim 1, wherein said remediation agent deliverysystem comprises a remediation agent storage tank, a conduit from thetank to the injection system and a pump system for pumping saidremediation agent from said storage tank through said conduit to saidinjection system for under pressure.
 6. The apparatus according to claim5, wherein said remediation delivery system further comprises a heatingsystem for heating said remediation agent.
 7. The apparatus according toclaim 1, further comprising a monitoring system for monitoring aselected physical or chemical property of said contaminated material inthe proximity of said trenching tool during operation of said apparatusand a system for adjusting said selected property of the contaminatedmaterial to a predetermined value.
 8. The apparatus according to claim7, wherein said system for adjusting said selected property comprises asystem for adjusting the amount of a constituent remediation agent insaid remediation agent injected into said contaminated material duringoperation of said apparatus.
 9. The apparatus according to claim 1,further comprising a volatile collection system for collecting volatilesubstances emitted from said contaminated material during operation ofsaid apparatus.
 10. The apparatus according to claim 1, wherein saidremediation agent is selected from the group consisting of a gas,liquid, slurry, and particulate solid.